The invention relates to a video retrieval system for retrieving video data. More specifically the invention relates to a video retrieval system with a retrieval means for retrieving trajectory data from a database as a response to a search query, whereby the search query is formulated on the basis of a search trajectory, which is representable and/or represented as a plurality of search segments, whereby the retrieval means comprises interpreting means for generating a plurality of minimum bounding areas, whereby the plurality of the minimum bounding areas covers the search trajectory or at least one of the search segments and whereby the retrieval means is realised for accessing the database by using at least one of the minimum bounding areas as a query area. Further the invention relates to a respective method and a computer program.
Nowadays, video cameras are often used for monitoring areas under surveillance. For monitoring more complex surroundings a plurality of video cameras are commonly employed, whereby the resulting data from the plurality of video cameras is viewed on-line or stored in data-bases and checked off-line. With a growing number of video cameras also the amount of the stored video data is increasing rapidly, which finally results in an enormous effort to search through the video data on- or off-line in case a time instance or location of a certain interesting event is unknown. Improvements are achieved by using systems for content-based indexing and retrieval of video data.
In the field of moving-objects-tracking it is known to use video content analysis algorithms (VCA) in order to support the search and the retrieval of video data, whereby in a first step the video camera images are segmented into static background and moving objects. In a further step these objects are tracked over time and the locations of the objects in each frame are extracted. The set of locations of each object over the life-time of the object is converted into a trajectory for each object. These trajectories can be stored in a database and used to search through the recorded video camera images.
The document U.S. Pat. No. 6,587,574 B1 discloses a system and a method for representing trajectories of moving objects for content-based indexing and retrieval of visually animated data. The method comprises the steps as elucidated above, whereby a descriptive data structure is generated on the basis of the extracted trajectories and whereby the descriptive data structure comprises at least trajectory data representative for the position, velocity and/or acceleration of the moving object.
A solution for an effective storage and retrieval of the video data is disclosed in the scientific article from A. Albers, R. Wijnhoven, E. Jaspers and P. d. With, Smart Search & Retrieval On Video Databases, 2006, Digest of Technical Papers, IEEE International Conference on Consumer Electronics (ICCE), Las Vegas, Nev., USA, January, 2006, which appears to be the closest state of the art. The authors propose in this article to use a hierarchical structure in the form of a so-called Re*-tree for indexing the video data, which is based on the idea of indexing the trajectories of moving objects by dividing the trajectories into segments, which are allocated to so-called minimum bounding rectangles. In order to optimize the data-structure, the authors propose to apply a spatial filtering on the trajectories prior to allocating the segments to the minimum bounding rectangles.